Recent industrial gear lubricant requirements in the areas of bearing wear and micropitting have created a need for new lubricant compositions. In order to meet these new requirements, new additive packages suitable for blending with various base stocks are needed. It is desirable that these new requirements be met without detracting from the positive properties of current lubricant compositions with regard to oxidative and thermal stability, load carrying/antiwear performance, corrosion protection, seal compatibility, demulsibility, and the like.
Typically, additive packages are directed to specific end uses, such as industrial gear oils (IGO) or automotive driveline fluids. The demands of one particular end use typically will be different from another end use. For instance, many industrial gears require a lubricant that can function in the presence of large quantities of water, as would be found in steel mills, or in the highly contaminated environment of a mine or quarry, while sustaining high loads, speeds, and operating temperatures. In contrast, certain automotive driveline fluids, such as a manual transmission oils, typically operate in the absence of water. As another example, industrial gears can be as large as 10 meters in diameter and incorporate spur, bevel, helical, and spiral bevel designs in an endless variety of configurations, whereas driveline gears may be orders of magnitude smaller and carry heavier loads.
It would be advantageous to identify a composition suitable as an additive system for multiple diverse uses, but it is difficult enough to formulate a lubricant for certain end use given the rapid changes in marketing requirements.
By way of example, there are a variety of industrial gear oil approvals that oil marketers find advantageous to claim on the labels of their industrial gear fluids. In Europe, a key approval is DIN 51517-3. This particular industry specification was recently revised by Deutsches Institut fur Normung (DIN) to include a bearing wear test known as the FE-8 Test. This test was originated by FAG, a German bearing manufacturer, and is described in method DIN 51819-3.
Additionally, in the last decade, a wear phenomenon known as micropitting has been a growing concern. Flender, a German gear manufacturer, has incorporated the FVA-54 Micropitting test as part of their fluid approval program. Micropitting is a fatigue phenomenon, occurring on surface-hardened gears. It is characterized by extremely small pits, each approximately 10 microns deep. Micropitted metal has a frosted or gray appearance. Depending on how the fluid performs in the three-stage FVA-54 Micropitting Test, the oils are rated as “high”, “medium” or “low” micropitting protection. Many oil marketers are currently requesting that industrial gear additive package suppliers demonstrate ample proof that their offering provides a high level of micropitting protection.
In addition to meeting these new requirements, industrial gear oils (IGOs) must maintain a specified level of performance in the typical bench tests that have been part of well-known industrial gear approvals like USS 224, AGMA 9005-D94, recently replaced by AGMA 9005-E02, Cincinnati Milacron, etc. The bench tests include, for example, Four Ball Wear (ASTM D2266), Four Ball EP (ASTM D2783), FZG Scuffing (DIN 51354-2), Timken (ASTM D2782), Copper Corrosion Protection (ASTM D130, ISO 2160), Oxidation Control (ASTM D2893, S-200), Rust Prevention (ASTM D665, ISO 7120), Static Seal Compatibility (DIN 53538-3), Demulsibility (ASTM D2711, ISO 6614, ASTM D1401), Foam Control (ASTM D892, ISO 6247), etc.
Given the enormous number of ingredients proposed for lubricant additive systems, it is a formidable task to find the right combination capable of meeting the number of new requirements desired in IGOs while maintaining traditional performance standards in other areas.
U.S. Pat. No. 4,511,481 discloses industrial lubricants stabilized with a triazole adduct of amine phosphates, providing oxidation stability, antiwear, and rust preventative performance.
U.S. Pat. No. 4,900,460 discloses sulfurized isobutylene reacted with dihydrocarbyl phosphates or phosphites as an extreme pressure and antiwear additive for lube oil compositions.
U.S. Pat. No. 5,225,093 is directed to a gear oil additive composition comprising (i) at least one oil-soluble succinimide and (ii) at least one carboxylic acid derivative composition produced by reacting at least one succinic acylating agent with a reactant selected from the group consisting of an amine and/or alcohol, wherein the succinic acylating agent has a substitutent group derived from polyalkene having a number average molecular weight of about 500 to about 100,000. These compositions contain on a weight basis 10-80 weight % of component (i) and 10-80 weight % of (ii) and the total of (i) and (ii) is 20-90 weight %. The patent is also directed to a major amount of a gear oil base stock containing the additive composition wherein the sulfur additives, phosphorus additives, and nitrogen additives are in proportions such that the composition possesses a weight ratio of sulfur to phosphorus in the range of about 5:1 to about 40:1, and a weight ratio of nitrogen to phosphorus in the range of about 0.05:1 to about 2:1. See also U.S. Pat. No. 5,176,840.
U.S. Pat. No. 5,328,619 is directed to an additive concentrate formed from a combination of (i) an oil-soluble amine salt of a dihydrocarbyl monothiophosphoric acid and (ii) at least one oil-soluble active sulfur-containing antiwear/extreme pressure agent, and (iii) one or more oil-soluble acidic organic additives, at least one of which is a hydrocarbyl phosphoric acid or a carboxylic acid. The concentrate contains one or more oil-soluble primary amines in an amount to give a pH in the range of about 6.0 to 7.0. See also EP 519 760 B1.
U.S. Pat. No. 5,358,650 is directed to a gear oil comprising a dialkyl ester of a dicarboxylic acid and PAO combination for the base oil and additive components, the latter comprising an organic sulfur-containing antiwear and/or extreme pressure agent, an organic phosphorus-containing antiwear and/or extreme pressure agent, a copper corrosion inhibitor, a rust inhibitor, a foam inhibitor, and an ashless dispersant. The gear oil has a boron content of about 0.0025 to about 0.07 wt. % and an S:P weight ratio of 8:1 to 35:1. See also U.S. Pat. No. 5,571,445, WO 1994/22990,
U.S. Pat. No. 5,500,140 teaches an oil soluble phosphorus- and nitrogen-containing composition having limited slip properties formed by reacting an O,O-dihydrocarbyl phosphorodithioic acid with an epoxide to form a product which is then reacted with phosphorus pentoxide to produce an acid phosphate intermediate which is then neutralized with an amine. The additive is considered by the patentee to be useful in lubricating oils to inhibit limited slip axle or differential noise. A composition comprising (a) an oil-soluble sulfur-containing antiwear/extreme pressure agent, and (b) a phosphorus- and nitrogen-containing composition such that the weight ratio of sulfur as component (a) to phosphorus as component (b) is in the range of about 1:1 to about 20:1. See also U.S. Pat. No. 5,573,696.
U.S. Pat. No. 5,547,596 is directed to a lubricant composition said to reduce the “chattering” of a limited slip differential of a car, obtained by adding a phosphate amine salt and a borated ashless dispersant to a base oil comprising at least one of a mineral oil and a synthetic oil, the composition having a nitrogen:phosphorus ratio of 0.5 to 1.0, and a nitrogen:boron ratio of 4 to 10, the phosphorus content being in the range of 0.15 to 0.40 wt %, the nitrogen content being in the range of 0.08 to 0.30 wt %, and the boron content being in the range of 0.01 to 0.04 wt %.
U.S. Pat. No. 5,691,283 teaches a lubricant for synchronized transmission or differential axle having a viscosity grade level of from SAE 75W-90 to SAE 85W-140 comprising a base oil containing at least (i) a Mannich base ashless dispersant; (ii) metal-free, sulfur-containing antiwear and/or extreme pressure agent; (iii) metal-free, phosphorus-containing and nitrogen-containing antiwear and/or extreme pressure agent, and (iv) overbased alkali or alkaline earth metal carboxylate, sulfonate or sulfurized phenate.
U.S. Pat. No. 5,756,429 discloses a lubricating oil composition comprising a base oil and sulfur, phosphorus, and nitrogen additives such that the ratio 100N/(S+P) is in the range of 4 to 10 by weight.
U.S. Pat. No. 6,046,144 discloses zinc-free antiwear hydraulic fluids and gear lubricating oils comprising thiophosphate antiwear agents, corrosion and rust inhibitors and an antioxidant composition comprising amine salts of alkyl phosphates and ethylenediamine, ammonium, or metal salts of alkylarylsulfonates.
U.S. Pat. No. 6,048,825 is directed to a lubricant composition comprising a synthetic base stock having a viscosity of 5.0 to 10.0 cSt at 100° C., an antioxidant selected from aromatic amines and hindered phenolics, at least one neutral phosphate, at least one dicarboxylic acid, at least one straight and/or branched chain monocarboxylic acid, and at least one triazole derivative. See also WO 1995/29214.
U.S. Pat. No. 6,180,575 discloses a lubricating oil having additives comprising an adduct of a substituted triazole with an amine phosphate in order to balance anti-wear and anti-rust properties. See also WO 2000/08119.
U.S. Pat. No. 6,605,572 is directed to lubricating oils with boron-containing compounds. The composition further contains sulfur and phosphorus such that the ratio of S to B to P is represented by the formula: S1+5B1+3P1>0.35, where S1 is the weight percent of sulfur in the composition, B1 is the weight percent of boron in the composition, and P1 is the weight percent of phosphorus in the composition. Furthermore, the composition contains “relatively low levels” of sulfur (0.01-0.25 wt %), and “relatively low levels” of phosphorus (up to 0.08 wt. %). See also WO 02/06930 A2 and U.S. Patent Application 2002/0147116 A1.
U.S. Patent Application 2003/0176299 A1 teaches a multifunctional lubricant comprising (a) at least one phosphoric ester of a C10 to C20 linear alkyl or alkenyl radical or a salt of such an ester, and (b) a polysulfide of general formula R—Sy—R, where y is from 2 to 8 and R is a C4-C18 tert-alkyl radical, wherein the ratio of a:b is between 0.01:1 and 1:1. See also WO 200166677.
WO 03/104620 A2 is directed to the problem of providing adequate engine lubrication and at the same time reduce catalyst contamination due to the use of phosphorus-containing compounds, where the phosphorus concentration is up to about 0.12% by weight, acting as extreme pressure and antiwear additives in engine oils. A composition is provided characterized by a nitrogen to phosphorus ratio of 0.3:1 to 4:1.
EP 1422287 A1 is directed to a lubricating composition containing 0.01-0.06 wt % phosphorus, 0-0.1 wt % sulfur derived from a base oil, and 0.01-0.15 wt % of sulfur derived from sulfur-containing additives, and characterized by having a P:S ratio of 1:(0.2-20). See also WO 03/020858 A1.
EP 391 653 B1 teaches the addition of a weak acid and an amine to sulfur-containing gear oils. The lubricating compositions comprise a lubricant, 1.7 to 20 wt % of a sulfur-containing extreme pressure (EP) or anti-wear agent, 0.1 to 10 wt % of a weak acid, and from 0.05 to 10 wt % of an amine. The weak acid is present in the amount of from 0.2 to 2 equivalents per equivalent of the amine, and the molar ratio of the sulfur in said EP/antiwear agent to the nitrogen in said amine is from 40:1 to 5:1.
EP 0 531 000 B1 is directed to lubricating oils and functional fluids formulated to meet certain American Petroleum Institute (API) requirements. The composition comprises a component (b) comprising sulfur at a level of at least 20 mass % and a component (a) comprising phosphorus, proportioned so that the mass ratio of sulfur in (b) to phosphorus in (a) is in the range of 8:1 to 30:1, further characterized as a finished lubricating oil having at least 0.5 wt. % sulfur as component (b).
EP 0 450 208 B1 teaches a lubricant comprising (i) one or more highly-active sulfur-containing extreme pressure or antiwear agents, (ii) one or more amines, (iii) one or more weak acids, wherein the mole percentage of sulfur in (i) to amino nitrogen in (ii) is 100:1 to 5:1 and is further characterized by having 0.2 to 2 equivalents of acid (iii) per equivalent of amine nitrogen in (ii).
EP 0 531 585 B1 discloses an oil-soluble additive concentrate comprising (a) a boronated Mannich base ashless dispersant; (b) a metal-free sulfur-containing antiwear and/or extreme pressure agent; (c) a metal-free phosphorus-containing antiwear and/or extreme pressure agent; and (d) an oil-soluble amine salt of an carboxylic acid, where the weight ratio of N in (a) to S in (b) is 0.00005:1 to 0.5:1 and/or the weight ratio of N in (a) to P in (c) is 0.005:1 to 5:1.
EP 186473 is drawn to an additive compound for lubricants and fuels containing amine linkages from mono- and polycarboxylic acids in the same molecule, produced by reacting a fatty carboxylic acid and at least one alkenyl- or alkylsuccinic acid and anhydride with at least one polyamine.
JP 7278142 (Application No. JP19940087388) discloses an additive having an olefinic polymer chain and obtained by reacting a dicarboxylic acid anhydride with a higher fatty acid and a polyalkylene polyamine.
JP 9235581 (Application No. JP19960302422) discloses a composition excellent in heat resistance, oxidation resistance, and abrasion resistance comprising a polyphenylene thioether, an acidic phosphate ester amine salt and a phosphate ester in a synthetic lubricating base oil.
JP 10316987 discloses a gear oil comprising a base oil, 0.05-8 wt. % sulfur compounds selected from hydrocarbon sulfides, sulfurized terpenes and/or sulfurized fats, and 0.1-6 wt. % phosphorus compounds selected from higher alkanol acid phosphates and/or their alkylamine salts.
Romanian Patent 118447 discloses an additive for heavy loading including succinimide and a dialkyl phosphate such as a sulfurized isobutene.
Other references of interest include U.S. Pat. No. 5,451,332 and EP 0 074 724.
The present inventors have surprisingly discovered a composition suitable as an additive system for diverse uses, such as for IGOs and for automotive driveline fluids. In preferred embodiments, the additive system may be combined with suitable basestocks to provide lubricants that meet the most recent industrial requirements for IGOs, without detracting from the positive attributes of currently available commercial products.